The P.I.'s work in progress deals with the anatomical organization of relay nuclei, ascending pathways and corticofugal control within the somatosensory system of normal and experimental (acute and chronic) rats, cats and monkeys. Progresses in the following main research projects are anticipated for the year 1977-1978: the origin and distribution of non-primary afferent fibers to the dorsal column nuclei of Rhesus monkeys using neuroanatomical techniques based upon the retrograde and the anterograde axoplasmic flow; the synaptic organization of the dorsal column nuclei of immature and adult normal and experimantal cats and rats; a re-evaluation of the organization of corticofugal projections to the dorsal column nuclei and spinal cord; neuroanatomical, neurocytological and neuropathological aspects, at both light and electron microscopical level, of degeneration in the dorsal column nuclei and spinal cord following peripheral nerve transection. BIBLIOGRAPHIC REFERENCES: Rustioni A. and Kaufman A.B., Identification of cells of origin of nonprimary afferents to the dorsal column nuclei of the cat, Exp. Brain Res. 27, 1-14, 1977. Moradian G.P. and Rustioni A., Transganglionic degeneration in the dorsal horn and dorsal column nuclei of adult rats, Anat. Rec. (abstract for AAAS meeting, Detroit, 1977) in press.